Swietenia Macrophylla)

Agronomía Costarricense 28(2): 37-51. 2004 PROGENY TEST ANALYSIS AND POPULATION DIFFERENTIATION OF MESOAMERICAN MAHOGANY (Swietenia macrophylla) Carlos Navarro1/*, Gustavo Hernández* Palabras clave: Swietenia macrophylla, heredabilidad, fitomejoramiento, evaluación de progenies, poblaciones naturales. Keywords: Swietenia macrophylla, heritability, tree improvement, progeny test, natural populations. Recibido: 07/01/04 Aceptado: 29/09/04 ABSTRACT RESUMEN The performance of open-pollinated Análisis de experimentos de progenies single tree families of mahogany Swietenia (familias) de una colección Mesoamericana de macrophylla from populations in Mesoamerica caoba (Swietenia macrophylla). El desarrollo de was evaluated in 3 trials established in northern progenies de árboles madre de polinización abier- Costa Rica. The trials at Upala and Lagartera ta de caoba, Swietenia macrophylla, fue evaluado (Los Chiles) contain families of Costa Rican en 3 ensayos establecidos en la Zona Norte de origin, while the Laberinto (Los Chiles) trial Costa Rica. Los de Upala y Lagartera (Los Chi- contains material from 6 Central American les) incluyen familias originarias de Costa Rica, countries and Mexico. Data on root-collar mientras que el de Laberinto (Los Chiles) presen- diameter, total height, survival, and Hypsipyla ta material de 6 países centroamericanos y Méxi- grandella attack were collected. The analysis co. Se recolectó información sobre diámetro a la indicate significant family and population base, altura total, sobrevivencia, y ataque de differences for height and diameter, but H. Hypsipyla grandella. Los análisis indican dife- grandella attacks were uniform over all sites. rencias significativas a nivel de progenie y proce- Heritabilities at 1.7 years for Upala were dencias para diámetro y altura, pero el ataque de 0.54±0.02, and 0.55±0.02 for diameter and H. grandella fue uniforme en todos los sitios. Las height, respectively; after this measurement this heredabilidades a los 1,7 años para Upala fueron trial was burned completely as a result of drought de 0,54±0,02 y 0,55±0,02 para diámetro y altura in El Niño year, so further measurements could respectivamente. Después de esta medición el en- not be made. Lagartera at 0.7 years presented sayo se quemó por completo, debido a sequías ba- heritabilities for diameter and height of jo el efecto de El Niño, razón por la cual no pu- 0.55±0.008 and 0.57±0.008. Laberinto presented dieron efectuarse mediciones posteriores. El heritabilities of 0.48±0.01 for diameter (2.9 ensayo en Lagartera, de 0,7 años, presentó here- years), 0.6±0.01 for height, 0.1±0.002 for H. dabilidades para diámetro y altura de 0,55±0,008 grandella attack; 0.07±0.002 for number of y 0,57±0,008. En Laberinto, las heredabilidades shoots, and 0.18±0.003 for stem form 2.7 years obtenidas fueron de 0,48±0,01 para diámetro (2,9 1/ Autor para correspondencia. Correo electrónico: * Tropical Agricultural Research and Higher Educa- [email protected] tion Center (CATIE), Turrialba, Costa Rica. 38 AGRONOMÍA COSTARRICENSE after planting. Flooding in 1998 damaged the años), 0,6 ± 0,01 para altura, 0,1±0,002 para el Lagartera trial, which was also severely attacked ataque de H. grandella; 0,07±0,002 para número by H. grandella. This resulted in very low de ejes, y 0,18±0,003 para la forma a los 2,7 años heritabilities, with large standard errors; de plantado. Las inundaciones en 1998 dañaron therefore its genetic values in the first el ensayo de Lagartera, que además fue severa- measurement are considered unreliable. The mente atacado por H. grandella. Esto se manifes- plantation recovered, and after 3 years genetic tó en heredabilidades muy bajas con errores es- values were comparable with the other 2 trials. tándar altos, por lo tanto los valores genéticos en Isolated mother trees produced slow-growing la primera medición se consideran poco confia- families in most cases, in comparison with the bles. La plantación se recuperó y después de 3 clustered ones or those in natural dense forests, años los valores genéticos fueron comparables suggesting inbreeding mechanisms. con los otros 2 ensayos. En general, los árboles madre que estaban solitarios, produjeron progenies de crecimiento lento, en comparación con las progenies de árboles madre que estaban en grupos o en bosque natural, lo que sugiere meca- nismos de endogamia. INTRODUCTION (Matamoros and Seal 1996), while current logging of natural populations for the Swietenia macrophylla is an important international market occurs in Brazil and Bolivia. tree species in the neotropics, it is found in the These tree species present a low rainforests between latitudes of 22o North and proportion of adult trees, which joined with a low 20o South of the Equator. Graham (1999) natural regeneration rate, increase their rareness. indicates that pollen from an ancestor of the The extensive harvest of S. macrophylla Meliaceae family was present in the Pliocene and for its valuable wood has resulted in high Miocene in Mexico, which led us to believe that concern over its conservation status and the species was present there many years ago. sustainable use (Proposed Amendment to CITES In Meliaceae, Swietenia is the most Appendix II 1997), and a strong focus of current important genus for wood production followed by research on these topics (Negreros and Mize Cedrela. Beginning in the 19th century and until 1994, Gullison et al. 1996, Snook 2003, Navarro now, the mahoganies have been the pillar of the et al. 2003). The FAO is establishing a network forest industry of Meso and South America. They to facilitate the genetic conservation of S. cover the neotropical territory from Mexico to macrophylla, and other species of the Meliaceae Brazil and Argentina, and the Caribbean Islands. family (Patiño 1997). S. mahagoni has already During the last decades, the Swietenia been heavily exploited, and both S. mahagoni natural populations have been severely affected and S. humilis were listed under Appendix II of and reduced by several factors, mainly due to CITES in 1992 (Patiño 1997). deforestation processes that diminish populations In 1994, CATIE and ITE (Institute of as well as selective logging that affects the Terrestrial Ecology) together with other genetic makeup of populations. institutions and the European Union support, The Mexican and Central American made a collection of mahogany germplasm in populations have been heavily exploited seven Mesoamerican countries. With this NAVARRO Y HERNÁNDEZ: Population differentiation of Mahogany 39 material studies of genetic variation were done, orientation and for thorough documentation of gene banks and progeny trials in Costa Rica and the collecting mission. Mexico were established. This work have been Collections were made from 42 different done considering the importance of using both mahogany populations, ranging from Mexico to molecular and quantitative markers for gene Panama. The number of trees sampled within conservation and breeding. populations varied according to its size and This paper investigates three major aspects: accessibility. Populations in each country were (1) The genetic variation throughout Mesoamerican located using the expertise of local collaborators populations and families of Swietenia macrophylla; and previous reconnaissance. The approximate (2) The growth variation in families and populations extent of each population was gauged as of mahogany; (3) The influence of collecting objectively as possible. isolated trees in their progeny performance. Trees were sampled along a transect, the The shootborer Hypsipyla grandella is a initial bearing was randomly selected. Mahogany Lepidopteran that co-evolved with some Meliaceae trees were either solitary or clumped. When trees species; it attacks preferentially; Swietenia, were clumped, collections were restricted to Cedrela and Carapa. Therefore, the adaptation of individual trees more than 100 m apart. To obtain different Swietenia populations to the shootborer maximum diversity and avoid seeds from related attack was also studied in these experiments. trees, only five individual trees per clump were collected. Up to a maximum of 50 trees were collected within each population along the MATERIALS AND METHODS transect. Only mature trees were selected. In some cases, populations were so sparse that only Collection solitary trees could be collected. Herbarium material was dried and Field collection of leaves, herbarium mounted at CATIE’s herbarium, and seeds were material and seeds from natural Swietenia dried and stored at the CATIE seed bank. populations were carried on. The populations Table 1 and figure 1 show the sites of sampled covered a wide range of environments, collections in Central America and Mexico. population densities and degrees of exploitation. This is the most extensive single-tree Prior to collection, general information collection of mahogany that has been made in was sought on: (1) climatic data - including this area. The Institute of Tropical Forestry in topography, geology, soil, vegetation, land use; Puerto Rico made an earlier provenance and (2) socio-economic data - including collection of S. macrophylla in 1964 and 1965. population, agricultural surveys, economic At that time, 14 provenances were collected in indicators, and information on the infrastructure, Mexico and Central America (Boone and roads and other means of transportation. Chudnoff 1970). This information was used to: Field trials ● Define eco-geographically distinct areas in the

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